A method of retrofitting a wind turbine having a tower and a first energy generating unit with a second energy generation unit is disclosed. The wind turbine has been operated for a first period of time at a first tower life rate and has a first tower life expectancy design value. The method includes determining the tower life of the wind turbine tower used during the first period of time; determining the remaining tower life of the wind turbine tower; replacing the first energy generating unit with the second energy generating unit; and operating the retrofitted wind turbine at a second tower life rate less than the first tower life rate so as to extend the life expectancy value of the tower beyond the first tower life expectancy design value.

A wind turbine rotor blade assembly which incorporates automatic-aerodynamic control of the blade pitch angle is disclosed. The airfoil of the rotor blade (110) is free to rotate about a strategically located longitudinal blade axis which forms the spar stub (115) and is connected to the hub (120) of a horizontal axis wind turbine. The location of this blade axis is precisely set with respect to the turbine blade's aerodynamic center and center of mass. By further incorporating a reflexed airfoil with positive pitching moment this arrangement aerodynamically induces an automatic and self-regulating alignment of the rotor blade pitch such that the airfoil is always operating at or near optimal angle of attack. Details are disclosed on these strategic relationships which enable the successful operation of the new blade design.

The invention provides a method for monitoring health state of blade root fastener, comprising the following steps: obtaining a sequence of acceleration signals representing the lateral vibration of the nacelle and a sequence of rotational speed signals representing the rotational speed of the rotor; analyzing the sequence of acceleration signals and the sequence of rotational speed signals to determine the amplitude of the nacelle at 2-time-frequncy of the rotational speed of the rotor; and determining the health state of the blade root fastener based on the amplitude. The invention also provides a system for monitoring the health state of the blade root fastener. Through the present invention, the health state of the blade root fastener can be determined with low cost and high precision, thereby improving the operation efficiency and operation safety of the wind turbine.

The method according to the invention for operating a wind turbine, comprising a tower and a rotor arranged at the top of the tower and having at least one rotor blade, which can be adjusted about a blade setting axis, has a first operating mode in which the at least one rotor blade has an operating angular position about the blade setting axis and a wind-force-dependent rotation of the rotor is converted into electrical power using a generator unit, which power is delivered from the wind turbine into an electrical network and/or stored, and a second operating mode in which the at least one rotor blade is adjusted by at least 60° and/or max. 110° about the blade setting axis relative to the operating angular position into a damping angular position, and a counter torque braking the rotor is controlled based on a vibration of the tower.

A method is provided for monitoring a pitch control system for a rotor blade of a wind turbine. The method comprises a step of receiving a blade pitch signal representative of a pitch position of the rotor blade, a step of determining a pitch deviation, based on the blade pitch signal and a blade pitch reference. If the determined pitch deviation exceeds a first pitch deviation threshold, a pitch deviation variable is increased by an amount that depends on the determined pitch deviation, the first pitch deviation threshold, and a duration of a time period during which the determined pitch deviation has been exceeding the first pitch deviation threshold. An error signal is provided when the increased pitch deviation variable exceeds a pitch deviation variable threshold.

A method of handling the pitch bearing unit of a rotor blade mounted to the hub of a wind turbine, the method including the steps of providing an extension assembly at the interface between the rotor blade and the hub, moving the rotor blade outward from the hub by means of the extension assembly to open a gap large enough to accommodate the pitch bearing unit while maintaining a connection between the rotor blade and the hub, and removing the pitch bearing unit through the gap.

An equivalent variable pitch differential control method and apparatus. The method includes: acquire a first control parameter and a second control parameter respectively by means of a static energy deviation PI control method; acquire an equivalent differential third control parameter using a dynamic energy deviation; and by taking a wind wheel measurement rotating speed and a wind wheel reference rotating speed as inputs, a proportion integration differentiation controller controls a wind generating set according to the first control parameter, the second control parameter, and the third control parameter, thereby making a wind wheel rotating speed follow the wind wheel reference rotating speed. A wind generating set is controlled in real time by combining first and second control parameters and an equivalent differential third control parameter to serve as parameter values of the proportion integration differentiation controller.

A method for constrained control of a wind turbine includes receiving a plurality of operating parameters corresponding to the wind turbine. The plurality of operating parameters includes a wind preview parameter and a plurality of constraint parameters. The method further includes generating a constraint parameter estimate corresponding to a future time instant for at least one constraint parameter of the plurality of constraint parameters based on the plurality of operating parameters and a wind preview model. The method also includes predicting an extreme event corresponding to the at least one constraint parameter based on the constraint parameter estimate. The method includes determining a control parameter value corresponding to a wind turbine control parameter among a plurality of wind turbine control parameters. The method also includes operating the wind turbine using a feedforward control technique based on the control parameter value to circumvent the extreme event.

The invention relates to a method for controlling a wind turbine in partial and full load. In order to avoid disadvantages of switching between partial and full load controllers, the wind turbine control system is configured so that both the partial and full load controller provides control action during partial and full load. For that purpose, the partial and full load controllers are configured with variable gains, wherein gain scheduling is performed so that the gain of partial load controller is larger than the gain of the full load controller during partial load and vice verso so that the gain of the full load controller is larger than the gain of the partial load controller during full load.

A wind turbine, including a hub, a blade, a blade bearing which is connected to the hub and which enables a rotational movement of the blade relative to the hub, and an adjustment device for adjusting a pitch angle of the blade, wherein the adjustment device includes at least one actuator and wherein an effective direction of an adjustment force of the at least one actuator when adjusting the pitch angle of the blade is tilted in an angle relative to a bearing plane of the blade bearing. One advantage of the wind turbine is that the adjustment force for adjusting the pitch angle is transmitted directly into the blade bearing or the bearing plane. Further, an offset of the attacking point of the adjustment force can be reduced or completely avoided.